1. Field of the Invention
The present invention relates to an image forming apparatus having a sheet storage unit for storing sheets with an image formed thereon, and to a sheet storage device.
2. Description of the Related Art
Some conventional image forming apparatuses such as copying machines and printers have a sheet storage unit for temporarily storing sheets with an image formed thereon inside the apparatus body.
Japanese Patent Application Laid-Open No. 2013-220905 discusses an image forming apparatus having a plurality of sheet storage units for temporarily storing sheets with an image formed thereon inside the apparatus body, in addition to a regular discharge tray that is disposed on the upper face of the apparatus body and is shared by a plurality of users. This image forming apparatus stores sheets in a different sheet storage unit for each job. When a user takes out the sheets stored in a sheet storage unit, the image forming apparatus performs user authentication, for example, through the use of an identification (ID) card. The image forming apparatus performs user authentication when the user causes an ID card reading unit provided on the apparatus body to read his or her ID card. When the user authentication has been successfully performed, the image forming apparatus discharges sheets, for which the user has issued a discharge instruction, from an opening portion to the outside of the apparatus body. In this case, when there is a plurality of target sheet storage units from which the sheets are to be discharged, the sheets stored in the respective sheet storage units are moved at the same time and then exposed from a common opening portion in a stacked manner. This enables the user to take out only his or her sheets with an image formed thereon, and collectively take out the sheets obtained from a plurality of jobs.
There may be a case where, when the sheets stored in the plurality of sheet storage units are to be exposed from the common opening portion, the sheets stored in the respective sheet storage units are different in length. In a configuration discussed in Japanese Patent Application Laid-Open No. 2013-220905, when the sheets in the respective sheet storage units are to be exposed from the opening portion by a predetermined length, the sheets stored in the respective sheet storage units are moved at the same time. In this case, since the sheets stored in the respective sheet storage units are different in length, it takes a different time in each of the sheet storage units to expose the sheets from the opening portion by the predetermined length. Therefore, there arises a situation where, when a first sheet stored in a certain sheet storage unit is exposed from the opening portion by the predetermined length and then stopped, a second sheet stored in another sheet storage unit is being moved. In this case, since the first and the second sheets are exposed from the common opening portion, these sheets may meet and contact each other halfway and then the moving second sheet may thrust out the stopped first sheet. Accordingly, the first sheet is exposed from the opening portion by a length longer than the predetermined length, causing a problem that it becomes hard for the user to collectively take out a plurality of sheets exposed from the opening portion. There has also been a problem that the first sheet falls from the opening portion with a large degree of thrust.